PLATYCEINID^. 701 



Remarlcs. — Resembling P. parvinodus in its general structure, but differ- 

 ing in the details. It is readily distinguished by its more elongate form, and 

 having the lower brachials to the top of the distichals always preserved in 

 the specimens by reason of their sutural union with the interradial plates. 



ORNIGBANULUS GROUP. 



Basals and radials forming a cup with moderately spreading sides, the 

 radial facets deep and wide ; arms short and very heavy throughout ; the 

 plates covered with coarse granules or irregular nodes. 



Platycrinus ornigranulus McChesney. 

 Plate LXVI. Fig. 8, and Plate LXVIII. Figs. 10a, b, c, 11a, h, and Ma, h. 



I860. McChesney ; Descr. New Palieoz. Foss., p. 5 ; and Trans. Cliicago Acad, of Sci., p. 3, Plate 5, 



Kg. 8. 

 1881. W. and Sp. ; Revision, Part. II., p. 73 (Proceed Acad. Nat. Sci. Phila., p. 247). 



Syn. Plati/cri/ius nodulosiis Hall, 1853 (not Goldfuss, 1833) ; Geol. Rep. Iowa, Vol, I., Part II., 



p. 541. 



Calyx of medium size, cup-shaped, moderately spreading ; the base but 

 .slightly convex, the lower part truncated, and the median portions abruptly 

 depressed for the reception of the column. Surface of plates entirely and 

 closely covered by small granules of irregular size and form, those nearest 

 the margins smaller and more closely arranged, those surrounding the col- 

 umn facet confluent and more or less ill-defined. Similar granules, but 

 smaller, cover the arms, each plate generally having two rows, transversely 

 arranged. 



Basals forming a very shallow saucer, of which the bottom is flattened 

 and only the outer margin is visible in a side view ; the columnar attach- 

 ment circular, and marked by distinct radiating strias; interbasal sutures 

 altogether obsolete ; basi-radial and interradial sutures slightly grooved. 

 Radials about as wide as long, the sides nearly straight, the width of the 

 lower face nearly equal to the length of the lateral ones, the upper faces at 

 the sides of the facets deeply notched. Facets large, occupying nearly one 

 half of the width, and fully two fifths the length of the plates ; slightly 

 thickened around the edges ; concave ; directed outward ; the margin of the 

 face crenulated. Costals triangular, short but wide, covering the whole 

 facet; their sloping upper faces concave. Distichals two, the upper one 

 larger than the lower, the latter giving off an arm to the outer side, and 



